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Pertussis
Pertussis, or “whooping cough”, is one of the most
common vaccine-preventable diseases. It is caused
by a bacterium that attaches to the upper respiratory
tract and releases toxins that cause inflammation
and swelling, resulting in a respiratory illness with a
characteristic ‘whoop-like’ cough.
Pertussis is an important cause of infant death
worldwide and continues to be a public health
concern even in countries with high vaccination
coverage. Estimates from WHO suggest that in 2008
about 16 million cases of pertussis occurred
worldwide, 95% of which were in developing
countries, and that about 195,000 children died from
the disease. It is one of the leading causes of death
by a vaccine-preventable disease worldwide.
Current high numbers of cases are also being confirmed in adolescents and adults from first world nations
- in whom a milder disease occurs, but still features a cough that may persist for many weeks. The reasons
for this increase are not completely understood, but waning immunity following vaccination and natural
infection are likely to be factors, as well as a raised awareness and testing contributing to the increase in
reported cases. There is also evidence that there are new mutations in the bacteria that existing vaccines
are unable to effectively control.
Pertussis is only found in humans and is spread from person to person. It is usually spread by coughing or
sneezing while in close contact with others who then breathe in the pertussis bacteria. Many infants who
get pertussis are infected by older siblings, parents or caregivers, who might not even know they have the
disease.
Symptoms
These usually develop within 5–10 days after being exposed,
but sometimes they do not appear for as long as 3 weeks.
The disease usually starts with non-specific cold-like symptoms
and maybe a mild cough or fever. After 1 to 2 weeks, severe
coughing can begin, resulting in a series of violent coughing fits,
over and over, until all the air is gone from the lungs, causing
forced inhalation with a loud "whooping" sound. This prolonged
coughing often results in vomiting and extreme tiredness, since
it can continue for 2 to 3 months.
In infants, the cough can be minimal or not even there. There
may be a condition known as "apnoea” - this is a pause in the
child's breathing pattern, often worrying for parents. Pertussis is
most dangerous for babies. About half of infants younger than 1
year of age who get the disease are hospitalized. Potential
complications include pneumonia, weight loss and in extreme
cases, brain damage.
Early symptoms can last for 1 to
2 weeks and usually include:
 Runny nose
 Low-grade fever (generally
minimal throughout the course
of the disease)
 Mild, occasional cough
 Apnoea — a pause in
breathing (in infants)
Later symptoms, from 2 weeks
onwards:
 Episodes of many, rapid
coughs followed by a highpitched "whoop"
 Vomiting
 Exhaustion from coughing fits
Diagnosis
When a child, or adult, is suspected of having whooping cough, laboratory testing of swabs of throat
secretions or blood samples are needed to confirm the diagnosis.
Treatment
Pertussis is generally treated with the early administration of antibiotics, before coughing fits begin, as this
may make the infection less severe. Treatment can also help prevent spreading the disease to close
contacts. However, after three weeks of illness they are unlikely to help because the bacteria will have
already gone, even though symptoms may well persist.
Infants younger than 12 months old are most at risk of serious complications from pertussis. Although
pregnant women are not themselves at increased risk of serious disease, those in their third trimester
would be considered for preventative immunisation, since they could in turn expose their newborn to
pertussis. This gives pregnant women higher levels of protection against whooping cough, which they will
then pass onto their babies. This is the best way to protect newborn babies against whooping cough until
they are old enough to be vaccinated.
Prevention
A vaccine exists for pertussis and is a usual component of childhood immunisation schedules all over the
world. While pertussis vaccine is the most effective means of preventing the disease, no vaccine is 100%
effective. If pertussis is circulating in the community, there is a chance that a fully vaccinated person, of
any age, can catch this very contagious disease. If you have been vaccinated, the infection is usually less
severe. If you or your child develop a ‘cold’ that includes a severe cough, or a cough that lasts for a long
time, it may be pertussis. The best way to know is to contact your doctor.
Protection from the vaccine is thought to last for between 3 to 10 years, and depends on a number of
factors such as: the type of vaccine, the number of doses you have had, and whether you have come into
contact with actual whooping cough bacteria. Adults, even those fully vaccinated against pertussis in
childhood, can get pertussis and transmit it to unvaccinated infants.
Natural infection with pertussis gives some protection (immunity) that can persist if you come into contact
again with the bacterium that causes whooping cough. Though this protection may last from 4-20 years,
long lasting immunity is not guaranteed.
Long-term travellers or expatriates may wish to seek advice from a health professional at their destination
and consider receiving a pertussis-containing vaccine formulated for adults and adolescents.
Is the Whooping Cough Vaccine Failing?
The vaccine used to immunise against whooping cough might have bred a more evolved strain of the
disease. Researchers from the University of NSW say that the bacterium that causes the potentially deadly
illness, appears to have evolved to overcome the vaccine used to fight it.
That vaccine works by locating a protein that had been identified as one of the key elements of the
disease. However, the study showed that about 80% of Australian whooping cough cases in 2012 were
caused by bacteria that did not contain this protein, the mutated pertussis thus gaining a selective
advantage over those carrying the protein.
Similar cases have also been found in France and the United States. The fact that they have arisen
independently in different countries suggests this is in response to the vaccine.
Although the new strain may prove more elusive to the vaccine, there was no current evidence that it is
deadlier. The study, which analysed more than 300 bacteria samples from across Australia, was published
in the Emerging Infectious Diseases journal.
Further evidence has emerged from UK studies that give statistics on just how pervasive this vaccine
failure is: despite most children being fully vaccinated for whooping cough, the infection is still present in
about a fifth of UK children visiting their doctor with a persistent cough - of these infected children 90% had
been fully vaccinated.
Another study, published in the New England Journal of Medicine, reported on the fact that vaccineresistant pertussis was now present in the United States.
This research suggests a vaccine failure rather than a failure to vaccinate.
Key Points
 Pertussis is a highly infectious disease caused by the bacterium Bordetella pertussis; it is
transmitted through the respiratory route. It is a major cause of illness worldwide and can
be particularly serious for babies, with severe complications and death occurring most
commonly in infants under six months of age.
 The WHO received reports of 136,036 confirmed cases of pertussis in 2013. However,
worldwide it is estimated that there are actually 16 million pertussis cases every year,
including approximately 195,000 childhood deaths.
 Pertussis is endemic worldwide and a recent WHO global review of pertussis identified
resurgences of disease in some countries with long standing vaccine programs and high
coverage.
 Pertussis is a major public health issue in Australia, with a notable rise in case numbers
since 2008 and the greatest increase in children under 10 years.
Sources
World Health Organisation
http://www.who.int/immunization/topics/pertussis/en/
US Center for Disease Control
http://www.cdc.gov/pertussis/outbreaks/trends.html
Nathnac UK
http://www.nathnac.org/travel/news/pertussis_au_130112.htm
Emerging Infectious Diseases: Rapid Increase in Pertactin-deficient Bordetella pertussis Isolates, Australia.
Volume 20, Number 4—April 2014
http://wwwnc.cdc.gov/eid/article/20/4/13-1478_article
____________________________________________________________________________________________________________
Written by Dr Adrian Hyzler MBChB MBA
Senior Medical Officer, Healix International
© Healix International 2015.
All rights reserved.
Published 5th May, 2015
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